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ERROR
PROOFING
TECHNIQUES
SUBMITTED TO:- GAURI MADAM
BY GROUP NO:- 4
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ERROR TRACKERS
DISHA 7511ANIKET 7516
DEEPALI 7518
PRIYANKA 7522
MEGHA 7525
MAHADEV 75__ VINAY 7564
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Definition: FMEA
failure modes and effects analysis
engineering technique used to define,
identify, and eliminate known and/or
potential failures, problems, and errors
from the system, design, or process before
they reach the customer
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Causes of errorschedule pressures
oversight
lack of testingchanging requirements
lack of structure
miscommunications
lack of prototypingincomplete CR
dependence on experience
dimension error
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Incomplete:taskspecified
butnotperformed
comprehensively
Omission:task
notperformed
Inadequate:tasknotspecified
comprehensively
Incorrect:
taskasspecified
resultsinerrors
Misperformed:
taskperformed
Incorrectly+++++++
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Type of FMEA How it works/what it does
Type of FMEA How it works/what it does
System FMEA Use VOC's to assign risks to thefailure of a system function
Design FMEA Looks at components of the
system
Assembly ProcessFMEA
Looks at impact of failures ofthe
manufacturing and assembly
process on the final system
Human Error FMEA Narrows process FMEA to lookat human mistakes and
omissions
in manufacturing
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Design Process FMEA
Similarto Assembly Process FMEA
question-basedanalysis
quickeranalysis
Analyzeandimprovethe
organizations design ordevelopmentprocess rather
thanaspecificproduct
?Process can be continuously improved to optimize
performance for many products
Decomposeproblemintodesign tasks instead of
Subassemblies++
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The 4 ComponentsofZDQ
ZDQfunctionsbycombiningfourelementarycomponents:
1. PointofOriginInspection
2. 100 % Audit Checks
3. Immediate Feedback
4. Poka-Yoke
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Inspection
The3basicapproachestoinspectionofprocessedproductare:
Judgement/StandardInspection
InformativeInspection
PointofOriginInspection
Thefirsttwoapproachesarewidelyusedandconsidered
traditional.
Only PointofOriginInspectionactuallyeliminates
defects.
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PointofOriginInspection
Focusonprevention,notdetection.
Oneofthe 4 basicelementsofZDQ.
DiffersfromJudgementandInformative:
Catcheserrors
Givesfeedbackbeforeprocessing
Noriskofmakingmoredefectiveproduct
DetectError
Feedback/Corrective Action
Processwith Zero Defects
Bycombining Checkand Dointhe ZDQapproach;the Doingiscontrolledsoit
cannotbewrong100% ofthetime!
Mayinclude: Switchesthatdetectmiss-fedparts
Pinsthatpreventmiss-feeding
Warninglights
Soundsignals
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ZDQ/Checkand Do/PointofOrigin
Inspection
PointofOriginInspection
Checkforoptimumprocessconditions
beforeprocessingisdoneanderrorscanbe
made.
Instantfeedback.
Correctionsmadebeforedefectsoccur.
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100% Audit Checks
PointofOriginInspectiononeverypiece.
Thesecondofthe 4 basicelementsofZDQ.
Differsfrom SQC inspection:
Doesnotrelyonsampling
Preventsdefects
Doesnotassumedefectswillstatisticallyoccur
100% Auditcheckseverythingontheline!
Zero Defects
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Quick Feedback
Errorcorrectionassoonaspossible
Thethirdofthe 4 basicelementsofZDQ.
Differsfromtraditionalinspectionapproachesthat:
Correctproblemsaftertheprocess
Addresstheproblemwhenerrorsarealreadydefects
Insomecasesneveridentifyanerrorhasoccurred
ZDQsendstheoperatorasignalandalarmsthe
personthatanerrorhashappened!
ZDQInspections = Immediate Feedback
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Poka-yoke
Mistake-proofingsystems
Thefourthofthe 4 basicelementsofZDQ.
Doesnotrelyonoperatorscatchingmistakes
Inexpensive PointofOrigininspection
Quickfeedback100% ofthetime
The machine shut
down. We must have
made an error!
BEEP!
BEEP!
BEEP!Most Poka-yokedevicesaresensoror jigdevices
thatassure100% complianceallthetime!
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The SevenGuidelinesto Poka- Yoke Attainment
1.) Quality Processes - Design Robustqualityprocessestoachievezerodefects.
2.) UtilizeaTeamEnvironment- leveragetheteamsknowledge,experience to
enhancetheimprovementefforts.
3.) EliminationofErrors -Utilizearobustproblemsolvingmethodologytodrivedefectstowardszero.
4.) Eliminatethe Root CauseofTheErrors-Usethe5Whysand2 Hsapproach
5.) DoIt RightThe FirstTime- Utilizingresourcestoperformfunctionscorrectlythe
firsttime.
6.) EliminateNon-Value Added Decisions- Dontmakeexcuses-justdoit!
7.) ImplementanIncremental ContinualImprovement Approach-implement
improvementactionsimmediatelyandfocusonincrementalimprovements;efforts
donothavetoresultina100% improvementimmediately.
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Poka-yoke
Whatis Poke-yoke?
A method that uses sensor or other devices for catching errors
that may pass by operators or assemblers.
Poka-yokeeffectstwokeyelementsofZDQ:
Identifying the defect immediately (Point of Origin Inspection)
Quick Feedback for Corrective Action
How effective the system is depends on where it is used: Point of Origin orHow effective the system is depends on where it is used: Point of Origin or
Informative Inspection.Informative Inspection.
Poka-yokedetectsanerror,givesa
warning,andcanshutsdownthe
process.
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Twotypesoferrorproofingdevices
POKA-YOKE
Control - eliminatesthepossibilityofa
mistaketooccur (automaticmachine
shutdown)
Warning - signalsthatamistakecanoccur(blinkinglight,alarm,etc.)
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Poka-yoke
Poke-yokeand PointofOriginInspections( Proactive Approach):
A fully implemented ZDQ system requires Poka-yoke
usage at or before the inspection points during the
process.
Poka-yokewillcatchtheerrors
beforeadefectivepartis
manufactured100% ofthetime.
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SomeexamplesofPOKA-YOKEdevices
Attachedgascap
Gaspumpnozzle
Polarizedelectricalplugandsocket
Discbrakepadwarningnoise
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Poka-yoke
Poka-yokeandInformativeInspection( Reactive Approach):
Checkoccursimmediatelyaftertheprocess.
Canbeanoperatorcheckattheprocessorsuccessivecheckatthenext
process.
Not100% effective,willnoteliminatealldefects.
Effectiveinpreventingdefectsfrombeingpassedtonextprocess.
Although not as effective as the Sourceinspection approach, this methodology
is more effective than statistical
sampling and does provide feedback in
reducing defects.
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Poka-yoke SystemsGovernthe Process
Two Poka-Yoke Systemapproachesareutilizedin
manufacturingwhichleadtosuccessful ZDQ:
1. Control Approach
Shutsdowntheprocesswhenanerroroccurs.
Keepsthe suspectpartinplace
when anoperationisincomplete.
2. Warning Approach
Signalstheoperatortostoptheprocess andcorrecttheproblem.
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Control System
Takeshumanelementoutoftheequation;does not
dependonanoperatororassembler.
Hasahighcapabilityofachievingzerodefects.
Machinestopswhenanirregularityisdetected.Theremusthavebeen
anerrordetected;themachineshutdownby
itself!
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Warning System
Sometimesanautomaticshutoffsystemisnotanoption.
A warningoralarmsystemcanbeusedtogetanoperators
attention.
Belowleftisanexampleofanalarmsystemusingdials,lightsand
soundstobringattentiontotheproblem.
Colorcodingisalsoaneffectivenonautomaticoption.
BEEP!
BEEP!
BEEP!
Imgladthealarm
wentoff,nowIm
notmaking
defects!
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Methodsfor Using Poka-yoke
Poka-yokesystemsconsistofthreeprimary
methods:
1. Contact
2. Counting3.Motion-Sequence
Eachmethodcanbeusedinacontrol
systemorawarningsystem.
Eachmethodusesadifferentprocess
preventionapproachfordealingwithirregularities.
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ContactMethod
A contact method functions by detecting whether a sensing
device makes contact with a part or object within the process.
Missingcylinder;pistonfully
extendedalarmsounds
ContactMethodusinglimit
switchesidentifiesmissing
cylinder.
Anexampleof aphysicalcontact
methodislimitswitchesthatare
pressedwhencylindersaredriveninto
apiston. Theswitchesareconnected
topistonsthatholdthepartinplace.
Inthisexample,acylinderismissing
andthepartisnotreleasedtothe
nextprocess.
Cannotproceed
tonextstep.
Cylinderpresent
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Physical Contact Devices
Limit Switches
Toggle Switches
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Energy Contact Devices
Photoelectricswitchescanbe
usedwithobjectsthatare
translucentortransparent
dependingupontheneed.
Transmissionmethod:twounits,
onetotransmitlight,theotherto
receive.
Reflectingmethod:PEsensor
respondstolightreflectedfrom
objecttodetectpresence.
Light
Transmitter Receiver
Object
Ifobjectbreaksthetransmission,themachineissignaledtoshutdown.
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Contact Device
Anexampleofacontact
deviceusingalimit
switch. Inthiscasethe
switchmakescontact
withametalbarb
sensingitspresence. If
nocontactismadethe
processwillshutdown.
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ContactMethods
Donothavetobehightech!
Passivedevicesaresometimesthebestmethod. Thesecanbeas simpleas
guidepinsorblocksthatdonotallowpartstobeseatedinthewrongposition
priortoprocessing
Takeadvantageofpartsdesignedwithanunevenshape!
A workpiecewithaholeabumporanunevenendisaperfectcandidatefora
passive jig. Thismethodsignalstotheoperatorrightawaythatthepartisnotin
properposition.
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CountingMethod
Usedwhenafixednumberofoperationsarerequiredwithinaprocess,orwhena
producthasafixednumberofpartsthatareattachedtoit.
A sensorcountsthenumberoftimesapartisusedoraprocessiscompletedand
releasesthepartonlywhentherightcountisreached.
Intheexampletotherightalimitswitchis
usedtodetectandcountwhentherequired
amountofholesaredrilled. Thebuzzersoundsalertingtheoperatorthatthe
appropriateamountofstepshavebeen
takenintheprocess.
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CountingMethod
Anotherapproachistocountthenumberofpartsorcomponentsrequiredto
completeanoperationinadvance. Ifoperatorsfindspartsleftoverusingthis
method,theywillknowthatsomethinghasbeenomittedfromtheprocess.
Ihaveanextra
part. Imusthave
omittedastep!
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Motion-SequenceMethod
Thethirdpoka-yokemethodusessensorstodetermineifamotionorastepina
processhasoccurred.Ifthestephasnotoccurredorhasoccurredoutofsequence,
thethesensorsignalsatimerorotherdevicetostopthemachineandsignalthe
operator.
Thismethodusessensorsandphoto-electricdevicesconnectedtoatimer. Ifmovementdoes
notoccurwhenrequired,theswitchsignalsto
stoptheprocessorwarntheoperator.
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Motion-SequenceMethodInordertohelpoperatorsselecttherightpartsfortherightstepinaprocessthe
sequencingaspectofthemotion-stepmethodisused. Thisisespeciallyhelpfulwhenusingmultiplepartsthataresimilarinsizeandshape.
Inthisexample,eachstepofthemachinecycleiswiredtoanindicatorboardanda
timer. Ifeachcycleofthemachineisnotperformedwithintherequired timeand
sequence,theindicatorlightforthatstepwillbeturnedonandthemachinewill
stop.
IndicatorBoardMachine
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TypesofSensing Devices
Sensingdevicesthataretraditionallyusedinpoka-yoke
systemscanbedividedintothreecategories:
1. Physicalcontactdevices
2. Energysensingdevices
3. Warning Sensors
Eachcategoryofsensorsincludesabroadrangeofdevicesthatcanbeuseddependingontheprocess.
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Physical Contact Sensors
Thesedevicesworkby
physicallytouching
something. Thiscanbea
machinepartoranactual
piecebeing
manufactured.
Inmostcasesthese
devicessendanelectronic
signalwhentheyare
touched. Dependingon
theprocess,thissignalcanshutdowntheoperation
orgiveanoperatora
warningsignal.
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Touch Switch
Usedtophysicallydetectthepresenceorabsenceofanobject
oritem-preventsmissingparts.
Usedtophysicallydetecttheheightofapartordimension.
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Energy Sensors
Thesedevicesworkby
usingenergytodetect
whetherornotandefect
hasoccurred.
Fiberoptic
Photoelectric
Vibration
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Warning Sensors
Warningsensorssignalthe
operatorthatthereisa
problem. Thesesensorsuse
colors,alarms,lightstoget
theworkersattention!
Thesesensorsmaybeused
inconjunctionwithacontact
orenergysensortogetthe
operatorsattention.
Color Code
Lights
Lightsconnectedto
Microswitches &
timers
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